Stabilization of low unsaturation isoolefinic copolymers



Patented Mar. 14, 1950 STABILIZATION or Low UNSATURATION isoomrmrc corona/mas Carl] F. Van Gilder,--Roselle, N. J., assignor to I Standard Oil Development Company, a corporation of Delaware No Drawing. Original application July 11, 1945,

Serial No. 604,519. Divided and this applioa- V tion December 29, 1948, Serial No. 68,081 h I F 8 Claims. (Cl. 200-4535) This invention relates to the stabilization of polymerized isobutylene and low unsaturation polymers generally, relates to means for maintaining the molecular weight of low unsaturation polymers and of polymers containing isobutylene, and relates especially to a polymerization process in which the polymer stabilizer is added to the polymerizate feed and taken up during the poly-:

Crafts type catalyst to yield polymers which may have Staudinger molecular weight numbers rang-Q ing from 1000 up to 500,000 or more. these polymers show a tendency towards instability, especially during heating, storage and mechanical working. It has been found that poly alkylated phenols such as 2,6,-tertiary butyl,

4 methyl phenol show a potent stabilizing action upon the polymers and are very effective in preventing breakdown of the polymers to lower molecular weight materials. But difliculty is encountered in incorporating these protective agents into the polymers, since the mechanical working necessary to disperse the protective agent into the polymer is very harmful to the molecular weight of the polymer and the harm is done before the protective agent can be put into the polymer in sufficiently Well dispersed homogeneous condition to be effective.

The polymerization reaction for the production of polymers containing isobutylene is an extreme ly sensitive one which is easily poisoned and in terfered with by the presence of even traces of impurities; 6 of a percent of 1% of normal butene will seriously reduce the molecular weight of the polymer produced. In the making of copolymers of isobutylene with such substances as butadiene, isoprene, and the like, the presence of the copolymerizable compound very greatly reduces the obtainable molecular weight. This is, with a high purity of isobutylene, a low tempera ture and a potent catalyst sufiiciently good to produce simple polyisobutylene with a molecular profoundly poisons the reaction, and the presence .7

However,

2 I 5 a of more than very small traces may result in" the; production of no more than the dimerizand trimer of isobutylene. Accordingly, in the poly-1' merization reaction, it has beenregardedasimaperativerthat the utmost possible purity offfe'e'd' materialsflbe had. v 4., Numerous substances are known which-rare reasonably effective antioxidation agents and stabilizers for natural rubber, the various -Buna's; and the like, but these compounds are found be Very severe, poisons'to the polymerizationxreej action.- (This is particularly true of the simple phenols which have been extensively used,- and to the amines, bothsimple and substituted;--these two j classes making ,upsubstantially all of, the; known anti-oxidants for natural rubber. {,1 According ate the present inventiomgit is found thatnthe polyyalkylated phenols, in s'p ite of the'pr'esence of the hydroxy group, *showwale most no poisoning effect upon thereaction and they may be admixed with the isobutylenic feed; and carried through the polymerization reaction unchanged and without influence on the poly: merization reaction; into a condition of very eX-. cellent, uniform, dispersion in thefinished poly;-. mer', whereby the protective action is'obtained from thevery moment of formation of the poly mer and noquestion of molecular weight -break down duringthe introduction of theprotective substance occurs.

Accordingly, the invention polymerizesg-iso-r butylene in the presence of the poly .alkylated phenol to produce directly an isobutylenic-epolye' mer yfullyprotected against molecular weight breakdown during storage, heating or mechanical working. Other objects and details of the in-. vention will be apparent from the following. de-, scription: a I 1 In practicingthe invention, an olefinic Inaterial is cooled toa low temperature, usually between 0C, and 169 C'., the preferred tem perature range being from 40 C. to ll0.C The olefinicor isobutylenic material may be cooled by a refrigerating jacket upon the com tainer or reactor, or by the direct admixture with the isobutylenic material of 2;, suitable refrigerant. For the. refrigerating jacket any low;- boiling liquid, boiling under either atmospheric pressure, vacuum or elevated pressureatthe de-, sired temperature may be used. For direct ad.-v mixture, such refrigerants as liquid propane yielding a temperature of 40 C. or liquidbr solid carbon dioxide yielding a temperature of -78 C. or liquid ethane yielding a temperature of -88C. or liquid ethylene yielding a tempera;

? ture of -1o3 c. are particularly suitable.

olefinio material may contain, in addition, a conmethallyl are particularly suitableii venient diluent; such materials as the lower halogen-substituted linear-chain compounds being particularly suitable.

These diluents are particularly desirable when the reaction material is cooled by a refrigerating jacket, since the presence of the diluents reduces the amount of gel formation and improves the characteristics of the polymer. may also be used in combination with an internal refrigerant, especially when the amount of internal refrigerant is relatively small, or when the heat of reaction volatilizes out most of the internal refrigerant.

For diluent materials, ethyl and methyl chloride, ethylene, dichloride, chloroform, and the like, are particularly suitable. Also, carbon disulflde is highly suitable. In addition, such hydrocarbon diluents as liquid ethane, liquid propane, liquid butane, liquid pentane; and the like are suitable, depending upon the polymerization temperature, since these substances may serve either as refrigerants or refrigerant .diluents, or simply as diluents, depending .upon the boiling point of the material and the polymerization temperature. i

' The polymerization mixture may consist simply of isobutylene or it may consist of isobutylene with arefrigerant or refrigerant diluent, as above pointed out. Alternatively, the polymerization mixture may contain a copolymerizable com- 1 pound for which the multi olefins are particularly suitable; such substances as butadiene, isoprene, piper'ylene, dimethyl butadiene, myrcene and di- The-copolymerization mixture may also-be a triple or quadruple component mixture, in which case such additionaltsubstances as styrene or alpha m'ethyl'styrene, para methyl styrene, alpha ethyl styrene, para ethyl styrene or the halogensubstituted styrenes, or the multi alkyl substituted styrenes are particularly suitable. In any of these mixtures, the significant amount of any onecomponent is as low as'from to 1%. That is, amounts of multi olefin as small as /2% produce significant and valuable differences in properties in the copolymer. Amounts of styrene or substituted styrenes as small as 1% produce significant diiferences; as do amounts of isobutylene as small as 1%. It may be noted that all of these compounds are substituted ethylenes.

Isobutylene may be regarded as dimethyl ethylj ene; styrene may be regarded as phenyl ethyl ene; alpha methyl styrene as methyl phenyl 1 atively minor consequence,' although some com- However, they 4 views, published for the American Chemical Society at Baltimore, in 1935, in vol. XVII, No. 3, the article beginning on page 327, the list being particularly Well shown on page 3'75, may be used. With mixtures contining isobutylene as the only polymerizable substance, gaseous boron trifiuoride is particularly useful and very convenient;

and gaseous boron trifluoride is usable for the pounds polymerize more easily than others, and l 1 some compounds require for copolymerization more potent catalysts than others. Itis not even necessary that the substitunts be hydrocarbons,

since various halogenated and oxygenated multiolefins copolymerize quite well.

For the polymerization catalyst, any of the conditions and dispersion.

production of copolymers with some of the multi olefins, although its catalytic powers are relatively very easily poisoned and are poisoned by some of the multi olefinic substances themselves, particularly butadiene. For the production of the copolymerizates, the liquid catalysts are preferred. .Liquid titanium tetra chloride is directly usable. The solid Friedel-Crafts catalysts must however be dissolved in a low-freezing, non-complex-forming solvent. Aluminum chloride in such a solution is particularly advantageous. Aluminum bromo chloride is soluble in a wider range of solvents, but is not as rapid a catalyst. Aluminum eth-oxy-chloride also is soluble in a widerrange of solvents, but is not as rapid a catalyst as simple aluminum chloride. Other Friedel- Crafts catalysts show similar variations.

' tuted compounds which have freezing points below 0 C.fare usable. It may be noted that it is not necessary that the freezing point of the catalyst solvent be below the polymerization tempera ture; it is merely necessary that the catalyst sol vent be liquid at a temperature maintainable within the polymerization reactor in order to obtain a rapid dispersion of the catalyst into the polymerization mixture. If the catalyst solvent is liquid at the polymerization temperature, the catalyst solvent and the Friedel-Crafts catalyst are quicklytaken up and dispersed into the reaction liquid under advantageous polymerization v It does not appear that the mere fact that the catalyst solvent may freezebefore it is dissolved is significant.

The catalyst, if gaseous, is conveniently bubbled through the polymerization mixture. If liquid,.the catalyst is conveniently applied to the polymerized mixtur in the form of a finely divided spray onto the. surface of the rapidly stirred, cold, olefinic material or in the form of a fine, high pressure jet into the body of rapidly stirred polymerization liquid. a

The reaction proceeds promptly to yield the desired polymer. In the case of isobutylene alone, the polymer obtained may be a more or less heavy, viscous oil with a Staudinger number; (that is, a molecular weight according to the Staudinger method) ranging from about 1000 up to 15,000 or 18,000 or it may be a heavy, plastic sticky semi-solid with a Staudinger number between 15,000 or 18,000 of about 27,000, or it may be an elastic solid with more or less cold flow and Staudinger molecular weight values from 27,000 to 500,000 or even higher. The simple polymer of isobutylene partakes more of the character of a fully saturated aliphatic compound than it does of an olefinic. compounds and the iodine number is extremely low, and in the higher molecular weight polymers is. so, low; as to be unmeasurable.

Copolymers of isobutylen6=and--=a 'multi-olefinare rarely produced with moleeular wei'ghts below it about 20,000 since at lower molecular-weights,- the' characteristic reactivity'with sulfur to develop an elasticwlimitand a substantial tensile strength does not-occur; apparentlybec'ause of thenecessity in each-moleculeofthe polymer of-a substan tial number of residual double linkages' from inalyst, anidazthislfactor ipermitstthem; to berpresent 1*: in the reaction mixture during the polymerizae.

tion procedure. It is to, thepresent unknown why the hindered phenols should all be more or less effective as protectiveflagentszin.the polymerrm =and itris not knowniawhether the new and tunexpected combinationof .properties in the hindered -phenols of=freedom from; effect onq'the Friedel terpolymerized multiolefirr sufficient to yieldsev eral cross linkages betweenadjacent molecules by the curingreaction; The preferredf molecular multi olefin liesxwithinxthe range between about 35,000 Rto abo'ut. .=80,000,-sin'ce lower molecular result from the :same structural: items in; the,

hindered polymers. 2 Weight-10f; the" 'copolymer of :isobutylene' and a anweights cure poorly and higher molecular weights.

process:poorlynthe polymer being too tough'and leatheryito-be milledrextruded; calendered and 1 otherwise processed. a 1

and the. multi olefin present inrminor-proportions; thetspreferred-'ratio;.being from'70 parts of isobutylene with 30 parts ofax-multi olefindown to 99.5 parts of isobutylenetwithrl5 part ofthe multi olefin, depending'upon: the ratio of copolymerization and; the. desired; amount. of -unsat- Particularlysuitablefor thisreaction aresuch: substancesas 2,4-dit. amy1 phenol;-.2-methyl-4-: "t;-butyl phenol, '2,3-dimethyl 6 trbuty1 phenol;

4-methyl-2.--t.-butyl phenol;- .4-methyl-2-n-buty1 phenol;- 2,4;6-trimethyl phenoLi2;4,6-tri-t;butyl. phenol, 4'-methyl-2,6--di-t.abutyl phenol and- 2,4-'

dimethykS-ftxbutyl pheno1.-

The polymerizationis'then conducted'upon'the isobutylenic materialin the presence'of a protec'-' tive agent, :The polymerization occurs promptly;

. merization-zis reached-the polymeriwis separated uration'imthe:polymer: The. resulting copoly-" mers may. have iodine numbers ranging. from about 0.5 "to about 50, thepreferred range being from l zto; about 20. Such copblymersshow: a"

unique 'reactivitygwith .sulfur in ascuring-reaction.

to yieldla. definite elasticalimit; a. ;tensile strength at break, .iranging from '1j'5001t0.AOOO-pQundsn er 1'; squarednch andr an.;elongation.at;breal ranging: ,1: a from 500% .,to -.;120Q%, these. materials, being highlyyrsatisfactory substitutes: for caoutchouc;

(natural- -rubber;)'..1 -;1

In practicing,therinvention; the desired olefinic:

mixture-is preparedand to-it:there is added from;

0.1% to:5i%i ofwthe'desired polyalkylated phenol; 1x and the: polymerization is-conducted; as .above outlined, intthe-presenceoftheflpolyalkylated phen0l.- v

For further: detailstof the polymerization ;proc.- ess anddetails-of the variousgavailable protective agents, crossreferenceis herewith. made to UQSM- 1'- PatentsiiaNo.12,356,127 and :No: 2,356,128 and t0 the applications .:of Smith &:Wi1son,'.TSerial No.-

604,520.,=.- filed. contemporaneously herewith, 'now x mpl -1 A mixture was preparedconsisting-"o'f isobutylene, having a'purityof approximately 98%' and approximately 045% (on the liquid isobutyl- "'ene) of 2,6 tertiary butyl 4, methyl phenol, and

cooled to a temperature of '-88 C. by liquid '--in the liquid isobutylene. The material was then polymerized by bubbling a stream of gaseous boron trifluoride through the cold material. -polymerization proceeded rapidly .to yield a solid The polymer of isobutyleneinwhich the alkylated phenol was absorbed. i The solid. polymer was recovered from the polymerization reactor by '-dumping the partially polymerizedmixture into abandoned, and-the-application of Joseph Nel-i terials which have protective effects; all of which sidues.

warm water to drive off. theunpolymerized re- Ihe polymer was-found upon test to .have a molecularweightof approximately 100,000.

A. similar sample of .polyisobutylene.prepared .by the sam procedure, but in the absence of the walkylated phenol. was .-alsoobtained-:and commay be addedato the; polymerization mixture,1

according "to" the present invention, before poly merization;

A particularly valuable. protective-agent isthe 2,6-tertiarysbutyl; -methyl, phenolzprepared by the interaction of para:cresol and isobutylene in a the presence'of: .conoentrated sulfuric acid, as. shownin more detail in U. S. :Patent' No. 1954-985;

I issued April 13;:1934; toil-lyym E. Buc.

It may be noted that-these: compounds:- all be- 1 long to the general classofhinderedphenols? in which thea'characteristics-aofthe phenolic group are altered, modified, and interfered with by the presence .of adjacent alkyl substituents. --The presenceof these auxiliary substituents, by-their between; the .phenol! .andy-the Friedel-Crafts cat:

(50 perature ofaapproximately-237iF. to yield the.

- resultsishovvnin Table I. Table I Unprotected Protected 6D Mnmg Time Polymer Polymer 0 100, 000 100,000 5 minutes.. 90, 000 99, 500 10 m1nutes 80, 000 )9, 300 10 minutes. 0, 000 ,200 70 minutes 00, 000 99,100 minutes. 55, 000 90, 000 minutes" 20,000 100 minutes 12, 000 )9, 000

influence. onthe phenolic group prevents reaction from the mixture in any convenient manner such? .as by discharging the polymerization mixture into warm water with .on'vvithout other'quenchingzand'a modifyingagents. The solid polymer-is then sep-z arated preferably .by filtration from the; water a i I slurry, dried and milled to bring it into: coherent T condition? ready for. compoundingand use.

1 ethane. The alkylated phenol. dissolved promptly.

nparison tests were made upon' the twosamples by milling them-upon theopen'roll mill at a-tem- I These comparative results: showtherexcellent 1 protective efiect of the ,alkylated aphenoli 1of the-..

aboorrsow r.

A mixture was fprepared'consisting of 97.5 parts of isobutylene of99%- purity and 2.5parts of isopreneof'96% purity. 'This mixture was diluted with 200 parts (by volume) of liquid ethane yielding a temperature of approximately 100 C. 'I'hismixture was divided into two parts, and

to one part was added'approximately 0.1% of 2,6-

tertiary butyl,4-methyl phenol; The twomixtures were separately polymerized by the addition 1 to each thereof approximately 50 parts by volume of a solution of aluminum chloride in methyl chloride containing approximately 0.8% of aluminum chloride. This amount of catalyst was suflicient to polymerize approximately 35% of the olefinic material present in each mixture. The solid polymer was then recovered by dumping the partially polymerized material into warm water to volatilize out the unpolymerized material and refrigerant, and the solid polymer was then strained out of the water solution, the respective portions being separately treated throughout.

The two portions of polymer were found to Y Example 3 A series of polymerizations were made including in each one of the following lists of protective agents:

2,4-di-t.-amyl phenol 2-methyl-4-t.-butyl phenol 2,3-dimethyl-6-t.-butyl phenol 4-methyl-2-t.-butyl phenol 2-methyl-2-n-butyl phenol 2,4,6-trimethyl phenol Q 2,4,6-tri-t.-butyl phenol 4-methyl-2,6-di-t.-butyl phenol 2,4-dimethyl-6-t.-butyl phenol one polymerization being conducted without the addition of any protective agent.

These several polymers were then placed in an accelerated aging test in the form of a hot air oven at 110 0., through which a slow current of hot air passed, and molecular weight determinations were made at two-day intervals. These determinations showed an excellent resistance to molecular weight breakdown and the results were indistinguishable from those obtained by J. F.

Nelson in the above mentioned contemporaneously-filed application. These results show that as far as the protective efiects were concerned, it

made relatively little difierence whether the protective agent was added to the polymerization mixture, or milled in after purifying of the polymer, except for the unavoidable molecular weight breakdown incurred during the milling required for the washing and processing.

* mantra; r

7 Similar results were obtained on a tri-polymer made up of 57 parts of styrene, 40 parts of isobutylene and 3 parts of iso-prene. This mixture was prepared and approximately 0.5% of the above listed protective agents Were added to var- "ious portions of the copolymerizate mixture which was then polymerized at 103 C. in the presence of liquid ethylene as a diluent refrigerant to approximately polymerization. The poly: mers were recovered separately and tested in the hot air oven, as above described. The several protective agents showed protective effects of the same order of magnitude and approximately the same order of efliciency as on the copolymer of isobutylene and isoprene.

Thus the process of the invention polymerizes an olefinic material in the presence of a protective agent in the form of a hindered phenol, or a polyalkylated phenol; preferably a 2,4,6 alkylated phenol to yield a polymerizate containing a protective agent which preserves the molecular weight from breakdown by mechanical working, heating or prolonged storage.

The invention claimed is:

l. The method of copolymerizing isobutylene and a multi-olefin having 4 to 10 carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor proportion of the multi-olefin and from 0.1% to 5% of a 2,4,6-trialkylated phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

2. The method of copolymerizing isobutylene and a multi-olefin having 4 to 10 carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor pro-portion of the multi-olefin and from 0.1% to 5% of 2,4,6-tri-tertiary butyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by

the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

3. The method of copolymerizing isobutylene and a multi-olefin having 4 to 10 carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor proportion of the multi-olefin and from 0.1% to 5% of 2,4,6-tri-methyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

4. The method of copolymerizing isobutylene and. a multi-olefin having 4 to 10 carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor proportion of the multi-olefin and'from 0.1% to 5% of 2,6-di-tertiary butyl-4- methyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and

164 C. by the application thereto of a Friedel Crafts catalyst dissolved in a non-complex -forming solvent which is liquid at the reaction temperature.

5. The method of copolymerizing isobutylene and isoprene having 4 to 10 carbon atoms'per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor proportion of the isoprene and from 0.1% to 5% of a 2,4,fi-trialkylated phenol and thereafter polymerizing the mixture at a temperature between C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

6. The method of copolymerizing isobutylene and isoprene having 4 to 10 carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutylene, a minor proportion of isoprene and from 0.1% to 5% of 2,4,6-tri-tertiary butyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

'7. The method of copolymerizing isobutylene and isoprene having 4 to carbon atoms per molecule comprising the step in combination of mixing together a major proportion of isobutyl- 10 ene, a minor proportion of isoprene and from 0.1% to 5% of 2,4,6-tri-methyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-complex-forming solvent which is liquid at the reaction temperature.

8. The method of copolymerizing isobutylene and isoprene having 4 to 10 carbon atoms per molecule comprising the step in combination of.

mixing together a major pro-portion of isobutylene, a minor proportion of isoprene and from 0.1% to 5% of 2,6 di-tertiary butyl 4 methyl phenol and thereafter polymerizing the mixture at a temperature between 0 C. and 164 C. by the application thereto of a Friedel-Crafts catalyst dissolved in a non-compleX-forming solvent which is liquid at the reaction temperature.

CARLL F. VAN GILDER.

No references cited. 

1. THE METHOD OF COPOLYMERIZING ISOBUTYLENE AND A MULTI-OLEFIN HAVING 4 TO 10 CARBON ATOMS PER MOLECULE COMPRISING THE STEP IN COMBINATION OF MIXING TOGETHER A MAJOR PROPORTION OF ISOBUTYLENE, A MINOR PROPORTION OF THE MULTI-OLEFIN AND FROM 0.1% TO 5% OF A 2,4,6-TRIALKYLATED PHENOL AND THEREAFTER POLYMERIZING THE MIXTURE AT A TEMPERATURE BETWEEN 0*C. AND -164*C. BY THE APPLICATION THERETO A FRIEDEL-CRAFTS CATALYST DISSOLVED IN A NON-COMPLES-FORMING SOLVENT WHICH IS LIQUID AT THE REACTION TEMPERATURE. 